The RAPD technique uses polymerase chain reaction (PCR) with single short random primers to identify polymorphisms in different lines. Because PCR is simpler, faster, easier to automate, and potentially cheaper than other genetic identification methods (such as RFLPs and isozymes), it has great potential utility for mapping human genes. However, a theoretical argument can be made that RAPD polymorphisms may not map to fixed locations. The purpose of this project is to test this argument by mapping RAPD polymorphisms in four different maize lines. These maize lines are being used because recombinant-inbred lines derived from them make the rapid mapping of polymorphisms possible. For the technique to be useful for mapping, polymorphic bands should map to the same location in all lines. Other experiments will explore the effects of competition between polymorphic sites during the amplification of DNA from Fl hybrids as well as the ability of polymorphic bands to cross-hybridize with other amplified sequences.